proton

I forgot that I asked two questions above. I'll check this thread to see if I got a response from those. Otherwise there's nothing of interest for me here. In my personal opinion its just a bunch of very poor arguements.

If that wouldn't overwhelm you then why do you think it would overwhelm someone else. That explanation wouldn't have overwhelmed me at all even before I started studying physics. I sincerly doubt that and I'm not about to dumb down my responses so that all 12 year olds will understand them. You didn't answer my question on momentum. Why? Merged post follows: Consecutive posts merged No. As I said that is clearly not true. Even physicists who have published journal articles against rel-mass have stated that what Klaynos claimed is not true. E.g. as a benchmark those authors note that 40%% of modern textbooks use rel-mass to some extent. If you claim otherwise then please provide hard evidence and not merely state a claims. Your counter example is as poor as mooeypoo's. I had explained that if only 60% of physicists don't use rel-mass then forcing everone to not use it is a bad idea. That's like that 40% of all men don't drink soda and 60% do and then serving 100% of them soda. If that is stil unclear then I'll say this - You don't logically force everyone to do what 60% of the group does merely because they could win a vote. In physics we don't vote. We each explain things in the best way we see fit. To explain something in what we believe to be a poorer way because 60% of the group wouldn't is a bad idea. I'm not commenting on arguements about rel-mass since arguements like that are useless. People form opinions on this subject religiously and its silly to argue about it so I refuse to. Since nobody is stating I cannot refer to other notions of mass I will continue to do so and will no longer read this very silly thread. If moderators feel otherwise then PM me. Proton - out!

It's hard to know how to explain something to a generic person. It's also hard to explain the HUP to someone who doesn't know probability. If I had a better understanding of your background I could try to modify it. Otherwise let me try it again - I will assume that you have a basic understanding of QM. By that I mean that there is a wave function associated with a particle. Let us denote this function as [math]\Psi(x,t)[/math] (assuming that the particle is restricted to move on the x-axis). The physical meaning of the wave function is that the square of the magnitude indicates where the particle is likely to be found when the position is measured. I.e. the probability is proportional to [math]|\Psi(x,t)|^2[/math]. To be precise - the probability [math]P(x, dx, t)[/math] of finding the particle about the point x in a region of width dx is [math]P_x(x, dx, t) = |\Psi(x,t)|^2dx[/math]. There is a similar relationship for the momentum which is called the momentum distribution function. Let that be labeled [math]\Phi(x,t)[/math]. Then Let that be labeled [math]|\Phi(x,t)|^2[/math] tells you what the probability of measuring the momentum to be p in an interval of width dp. I.e. [math]P_p(p, dp, t) = |\Phi(p,t)|^2dp[/math]. If the wave function is large at x and smaller elsewhere the particle said to be localized. The more localized the posotopm is the less localized the the momentum is. The relationship between the two is given by HUP relation I posted above. How's that?

Heat is the energy transferred from one object to another by virtue of their difference in temperature. I suggest this definition does not include radiant energy because an object radiates electromagnetic energy regardless of whether another object is there to intercept it.

We use all of our senses to experience the world. That means that we can use electrons to interact with matter in a way that is detectable by our senses. Given a theory of electrons we can construct experiments to see if our ideas conform to reality. If the experiment works like we planned then we have more confidence in our ideas. If they don't then we modify them. To explain all the reasons why physicists believe in the existance of electrons would take a lot of room in this thread. You can find that information on the internet. Actually photons do bounce off electrons (all charged particles to be exact). The process is called Compton scattering.

That is absolutely not true. If you and others keep posting poor/erroneous arguments then don't claim I'm belaboring the point when I address/correct them. E.g. it was Martin who started this thread. I was happy with what I wrote. It was he who came along several days later with the false impression that You want us to use "mass" to mean E/c^2 and you who contributed to prolonging it with notions like If what I mean by mass is different from what you mean by mass ... Both comments are so wrong its as if neither of you read or paid attention to what I wrote. E.g. it's crystal clear that you erroneously thought that I was saying that when I used the term “mass” I was going to mean “relativistic mass”. That is incorrect. Why you, and the sarcastic and irritating iNow, came to that conclusion is beyond me since I’ve never written anything that even remotely suggested that. My posts in the other thread are examples demonstrating that is not the case in fact. People come here to learn and I explain things such that they don't walk away with erroneous ideas. I have over a decade of first hand experience seeing all sorts of errors people make because they are merely told that "mass = rest mass." That is why I explain more than you choose to - Period. If you want to ban me from this forum for explaining in more detail than you do then please do so and stop wasting my time with this thread. Also please stop making these false assertions. That is hardly the case. E.g. there are are huge variety of when this kind of thing might come up. For example; someone might simply ask "Does light have mass?" You would write "No" whereas I would write "A photon has zero rest mass, since it can't be at rest, non-zero relativistic mass since it has momentum, non-zero passive gravitational mass, since its effected by a gravitational field and non-zero active gravitational mass since it can generate a gravitational field." Please explain how that overwhelmed you? I was going to make an point above by asking mooeypoo a question. He decided not to answer it. I'll ask you - What does the term momentum mean?

The Heisenberg Uncertainty Principle (HUP) relates the standard deviations of collections of data of a two conjugate variables taken from a series of experiments. Example: suppose you have a wave function [math]\Psi[/math](x, y) which represents a particle restricted to move along the x-axis. Execute a large number of position measurements, each time starting with the same wave function. Let xi represent the position recorded during the ith experiment. The probability of measuring the position of the particle in the range x to x+dx is [math]|\Psi|^2[/math]. The expectation value of finite number of x measurements is defined as [math] <x> = \sum x_i P_i[/math] where Pi is the probability of measuring xi (in the range x to x+dx) Also form the expectation of x2 [math] <x^2> = \sum x^2_i P_i[/math] For a continuous variable such as x the sums become integrals. Now form the quantity [math]\Delta x[/math] defined as [math] \Delta x = \sqrt(<x^2> - <x>^2)[/math] [math]\Delta x[/math] is called the uncertainty in x. Now do the same thing for momentum. There is a momentum wave function which is the Fourier transform of [math]\Psi[/math](x, t). Call this [math]\Phi[/math](x, t). Use this similar to the above to get [math]\Delta p[/math]. The HUP states that [math]\Delta x \Delta p \le \hbar/2[/math] Simply put, [math]\Delta x[/math] is a quantity which gives a measure of the spread of possible position measurements as reflected in a data set that would be obtained from a large number of identical experiments of the measurement of x when the system is initially in the state [math]\Psi[/math](x, t). Similarly, [math]\Delta p[/math] is a quantity which gives a measure of the spread of possible momentum measurement as reflected in a data set that would be obtained from a large number of identical experiments of the measurement of p when the system is initially in the state [math]\Phi[/math](p, t). The HUP relates these two values by the above inequality. Important - It can't be stressed enough that the value of the uncertainty is not determined by the measurement process and thus not determined by how the measurement is done. It is a value that is intrinsic to the initial state of the system. Its value is uniquely determined by the wave function of the system. Different wave functions give different uncertainties. No matter how good your measurement process is, or your instruments are, you cannot reduce the uncertainty in the measured value. And when you measure a variable it does not reflect the precision of the measurement People almost always seem to have the wrong idea about what the HUP is all about and this wrong idea is a result of the wrong idea of what uncertainty is. If you keep in mind that the uncertainty in a quantity is the same thing as the standard deviation and is thus statistical in nature then you'll be on the right track. It’s misleading to say that the measurement in one value affects the uncertainty in the other value. The actual situation is that the wave function determines the uncertainty and if you change the wave function so as to decrease the uncertainty then you end up changing the Fourier transform of the wave function and that results in an increase in the uncertainty of the conjugate variable.

Can you rephase your question please? I don't know what the weight of the body will actual? means.

I did a search and found this http://www.thorlabs.com/navigation.cfm?Guide_ID=132&gclid=CJal_OmEs5sCFQxM5Qod0At2Qg So it seems that lens for IR do exist, at least in the 1 to 16 µm spectral range. Cool! I never knew that! That's what I love about posting in forums. You never know what you might learn simply because I never asked a particular kind of question. Thanks for asking this question Externet!

You made a mistake here. In fact most physcists are ingorant on this point. Relativistic mass is not defined as mrel = E/c2. It's defined as the quantity mrel in p = mrelv. In general these quantities are not the same. E.g. for a single photon mrel = E/c2 is an equality, not a definition.

That's like asking what can cause a body to move. Consider a line of charge at rest on the x-axis of the inertial frame S. There is no flow of charge in this frame. Now transform to an inertial frame S' moving in the direction of the +x axis. In S' there is a current, i.e. a flow of charge.

Not according to Martin who said We at SFN have liked to keep it simple and have just one concept of mass, .... However that was a vague statement and needs clarification. Merged post follows: Consecutive posts merged Mock language? What is that supposed to mean? And why do you keep implying that I don't explain myself? I have stated quite clearly in nearly all posts in this and the other thread that I clearly state what I'm referring to when I do so and you insist on ignoring that fact and keep insinuating that I'm not precise in my language. Frankly it's starting to get very irritating. And why do you keep insisting that this is "my" language? You clearly have a somewhat limited knowledge on this subject. Pick up a few relativity texts and do some more reading. Ever read A first course in general relativity by Bernard Schutz? Ever read Rindler's text? Ever read Gravitation by MTW? Ever read Ohanian's GR text? Ever read Mould's? Ever read Peeble's cosmology text? Ever read the American Journal of Physics? You also failed to answer my question on momentum. Why is that? Don't you know how it's defined? I asked that question to make a point. If nobody responds to it then I can't make the point.

That was a very poor counter example mooeypoo. I will not get dragged into a debate. I asked one question and am awaiting a response from the moderators. What you personally choose to do is your buisness. What don't you understand? Nothing I've ever posted was anything but 100% clear about what I was talking about. In those instances where I used m to mean relativistic mass I stated so explicitly. I always have and I always will. I've already stated that above. Did you not read it? As far as definitions go, what does the term momentum mean? I asked this above and got no response.

Thanks for the correction. Notice that it doesn't speak of protons, presumably because protons are systems composed of quarks and as such as a non-zero invariant mass. A system composed of two photons moving in opposite directions also has a non-zero invariant mass.

Bad idea. So because 60% of modern texts don't use rel-mass you want to force 100% of the people here not to? Unwise. I asked a very clear question and have not yet gotten an answer; are you going to prevent people from talking about other concepts of mass. Do you understand why I mention what I do? It's for one single reason - to prepare people for what they will read in the physics literature and for no other reason. I mentioned to cameron what I did about mass of light because he might want to learn GR or cosmology one day and that's what he'll encounter. I don't wish to post at a forum where people are banned from talking about certain articles that appear in the American Journal of Physics or various physics texts (even advanced modern ones) because people here are ingorant of such usage.

I asked people not to get personal. I don't get personal and I expect others not to. Address the physics and not who is posting the physics. But that has nothing to do with qualifications. Ad hominem attacks are a completely different subject that qualifications. I asked you if you were a physicist because I wanted to know what makes you qualified to make such a claim. Simply reading other people's claims on forums like this cannot inform anyone as to what is actually used by physicists. My question is quite relevant since if you're not a physicist then I have no reason to take anything you say on such claims seriously. Someone who is a physicist has the minimum qualifications to know whether physicists use a concept or not or what is found in various physics journals. So fine. You're not a physicist. It's clear from your responses anyway, i.e. all ad hominems and nno physics content. Frankly I find your insulting attitude rather disturbing. It's a shame that such a poor attitude is tolerated.

That is subject to opinion. You didn't answer my question. Are you a physicist?

Frankly I'm not interested in such an opionions since it's dead wrong. Read the article I linked to which did a study on its usage in the modern physics literature. I assume that you used the term practically so that you wouldn't be accused of claiming that Bernard Schutz and Wolfgang Rindler are not worth their salt? By the way, for a suggestion to have any worth one should know the source. Are you a physicist? Have you ever done a study to determine what percentage of physicists use relativistic mass? Please folks. Let's not get personal. Please stick to the subject matter. Discuss the subject and not me. It's very distasteful to get so personal.

No. First off its not a modern textbook. In the second place I don't know who wrote it and in the third place it doesn't even provide a definition. The person who wrote that web page is clearly using the term in a vauge sense, as most people do. Notice that he only said I even agree with that statement. That doesn't mean I know what the author has in mind for a definition. Notice that he didn't refer to electrons? What are we to conclude as to whether an electron is made of matter? My point is that different people use this term in different ways. It's not a term which requires a technical definition. Nobody ever really needs to use such a term in fact. Consider the context in which it is used too. How would you determine whether something was matter by examining the stress-energy-momentum tensor? For example; if there is a static magnetic field in frame S (where in S there is no electric field) then the momentum density in this frame is zero while the energy density is non-zero. Typically physicists like to think of things which have energy and for which there is a rest frame as something for which a mass can be defined. The proper mass density is found by transforming to the zero momentum frame, calculating the energy density and then dividing by c2. For the magnetic field in S this will give something which is non-zero. Would you call this magnetic field "matter"? Would you say that the field has a non-zero mass density?

I don't understand your point. Can you clarify please. Merged post follows: Consecutive posts merged That depends on a few things. It most of all depends on how you define mass. Then it depends on what aspect of mass you're referring to. It also depends on the particular object. For example; you wouldn't measure the mass of a black hole the same way you'd measure the mass of an electron. The relativistic mass also depends on the orientation of the body relative to its velocity since the rel-mass is a function of the stresses that its under. Typically the idea of mass is its measurement of its resistance to changes in momentum. This is what's known as Weyl's definition of mass. I.e. its the m in p = mv. This is close to being how Newton defined mass too. It depends on the definition of mass. For example; if you're interested in the active gravitational mass of the body, i.e. the mass as the source of gravity, then you're measuring how the body generates a gravitational field and how it affects the geodesics of bodies moving in its field. The gravitational field of a body is a function of its velocity so the faster it's going the stronger its gravitational field. It's a bit more complex than that though. There was an article on this subject in the American Journal of Physics. The article is called Measuring the active gravitational mass of a moving object, D.W. Olson and R.C. Guarino, Am. J. Phys. 53(7), July 1985. The abstract reads All I'm saying here is that I don't want to be in a position where I'm prohibited from mentioning/discussing articles like this. If the forum bans all mention of the concept of rel-mass then it is that which I object to. I also think that if its okay to discuss rel-mass when someone is interested in it then it would be a bit irritating to see someone start in with a debate everytime it comes up. I understand that people can be fanatical about getting rid of all mention of rel-mass so its for that reason I mentioned those two URLs. I really dislike arguing about semantics. All i want to know is whether I'll be prohibited from discussing concepts of mass other than rest mass.

So what? Why do you make such a big deal of it. I found the first reference by searching online and then copied it from my copy. After that I looked in the author's EM book which I have so I then added it. I didn't realize that adding it would confuse you so much, especially since the author's are the same. Actually the first instance makes it clear that both authors agree with the usage and that the second usage is found in a more advanced text on the subject. It's obvious what my point was. To demonstrate that such an interpretation, e.g. that of Einstein's, is found in modern physics texts.

You misunderstood my comments. Perhaps Martin did as well. If so then perhaps I won't need to leave. In the mean time I challenge you to find a post I wrote in which I was not 100% clear as to what I meant by “mass.” Recall what I said to cameron. One simply could not have misunderstood what I meant. I do not, nor have I suggested that I will, use "mass" unqualified to mean "relativistic mass." I was quite clear as to what I said. I merely find it to be pain in the butt to keep writing relativistic mass everytime I refer to it. I feel that its easier to write mass and simply note what I mean by it. That's the reason particle physicists use the term mass unqualified to refer to proper mass, i.e. it's simply too unwieldy to keep using the "proper" qualifier. Let's be clear on what I said. I made the following points 1) The notion that concept of relativistic mass has been removed from physics is a widely held misconception among both physicists and laymen alike. 2) If someone objects to someone using relativistic mass then they shouldn’t start a debate about it but merely post the two URLs and suggest they read them. 3) It is not uncommon to see mass used in other contexts such as active/passive gravitational mass. This seems to be a widely used term in cosmology. Even in Schutz’s GR text he states that mass and energy are the same thing. This is the essence of relativistic mass. Also the concept of the inertia of stress is becomming more visible in the relativity literature. This is not refected in the simply use of "rest mass" to refer to a property of point particles. 4) I mentioned instances where authors refer to radiation having "mass" so that newbies won’t be confused about it if/when they encounter it. Martin seemed to think that I was attempting to “reform” people’s language in physics. That is the furthest thing from the truth and there is zero justification for such an accusation based on what I posted. Perhaps his mistake in that respect confused you. I simply don’t care what people mean by “mass” since its always clear from the context what they mean. Newcomer’s should have the maximum amount of information at their disposal to prepare them for what they might encounter in the future. Schutz’s GR text is one of the most highly used, respected, and recommended texts in GR today and Schutz does say that energy and mass are the same thing and he doesn’t use the term relativistic mass. Ohanian refers to the mass density of radiation. I was making these points clear for Cameron. We have no idea what Cameron wants to learn. If/when he tells me that he doesn't want to know anything beyond rest mass then I will never mention it to him again. You made many claims in your last post which are quite far from the truth. I never suggested that I want people to use that. I'm a bit dismayed that you feel the need to get personal here. What you claim is not true. I may be new in this forum but I'm far from being new to physics or to discussion forums. I don’t claim to be an authority of anything either. You read something into my responses that was never there. I know many physicists' date=' a few of which are authorities in their field either. But most physicists I know would never make such a claim. For example; what field are [i']you[/i] an authority in? Being educated and knowledgeble in a field does not make one an authority and I've made no such inferences or claims. I’ve been a physicist for 20 years. I've chosen my field o study/research to be relativity almost 20 years ago. I’ve been discussing relativity on the Internet for a good 13 years too so I know when newbies get confused. Young? Gee! Thanks. But I’m almost 50 yo. And please stop making false accusations like this. I have no mission. Just because I don't want people to force their views on be does not mean I want to force mine on others.

I have no desire to change what terms people use. I only object to when people try to change mine because its fashionable. You won't be confusing newcommers because they don't know what you've chosen for them yet. Sinced I choose not let people choose how I explain things it's best I leave. Thanks.

Yes. It appeared in two different texts. One of basic physics and one on EM. That's why I posted them both. And since the author is the same it was obvioius that they were not independent instances so I didn't see the point in mentioning that point. Nobody suggested it was standard, certainly not I.

The expansion means that different galaxies are moving relative to us and its that motion which results in time dilation.